[FFmpeg-devel] [PATCH] libavcodec/h264_parse: don't use uninitialized value when chroma_format_idc==0

[Mark Wachsler]

When parsing a monochrome file, chroma_log2_weight_denom was used without
being initialized, which could lead to a bogus error message being printed, e.g.
  [h264 @ 0x61a000026480] chroma_log2_weight_denom 24576 is out of range
It also could result in warnings using AddressSanitizer.
---
 libavcodec/h264_parse.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/libavcodec/h264_parse.c b/libavcodec/h264_parse.c
index 3d20075f6a..d9a3a0c154 100644
--- a/libavcodec/h264_parse.c
+++ b/libavcodec/h264_parse.c
@@ -34,21 +34,22 @@ int ff_h264_pred_weight_table(GetBitContext *gb, const SPS *sps,
 
     pwt->use_weight             = 0;
     pwt->use_weight_chroma      = 0;
-    pwt->luma_log2_weight_denom = get_ue_golomb(gb);
-    if (sps->chroma_format_idc)
-        pwt->chroma_log2_weight_denom = get_ue_golomb(gb);
 
+    pwt->luma_log2_weight_denom = get_ue_golomb(gb);
     if (pwt->luma_log2_weight_denom > 7U) {
         av_log(logctx, AV_LOG_ERROR, "luma_log2_weight_denom %d is out of range\n", pwt->luma_log2_weight_denom);
         pwt->luma_log2_weight_denom = 0;
     }
-    if (pwt->chroma_log2_weight_denom > 7U) {
-        av_log(logctx, AV_LOG_ERROR, "chroma_log2_weight_denom %d is out of range\n", pwt->chroma_log2_weight_denom);
-        pwt->chroma_log2_weight_denom = 0;
-    }
+    luma_def = 1 << pwt->luma_log2_weight_denom;
 
-    luma_def   = 1 << pwt->luma_log2_weight_denom;
-    chroma_def = 1 << pwt->chroma_log2_weight_denom;
+    if (sps->chroma_format_idc) {
+        pwt->chroma_log2_weight_denom = get_ue_golomb(gb);
+        if (pwt->chroma_log2_weight_denom > 7U) {
+            av_log(logctx, AV_LOG_ERROR, "chroma_log2_weight_denom %d is out of range\n", pwt->chroma_log2_weight_denom);
+            pwt->chroma_log2_weight_denom = 0;
+        }
+        chroma_def = 1 << pwt->chroma_log2_weight_denom;
+    }
 
     for (list = 0; list < 2; list++) {
         pwt->luma_weight_flag[list]   = 0;
-- 
2.14.1.581.gf28d330327-goog